Semiconductor dice or chips are typically contained in semiconductor packages. This is sometimes referred to as the first level of packaging. The package is required to support, protect, and dissipate heat from a die, and to provide a lead system for power and signal distribution to the die. The package is also useful for performing burn-in and full functionality testing of the die.
In general, conventional plastic and ceramic packages incorporate several common elements. These common elements include a sealed package enclosure, a die attachment area, bond wires for establishing electrical communication with bond pads on the die, and a lead system for the package. One shortcoming of a conventional semiconductor package is that a peripheral outline (i.e., footprint) of the package is typically much larger than that of the die contained within the package (e.g., 10.times. or more). In addition, the manufacturing processes for conventional packages are relatively complicated, and require large capital expenditures.
Another type of package is referred to as a ball grid array (BGA) package. With this type of package, a substrate formed of a glass filled resin, or similar material, includes patterns of conductors in electrical communication with arrays of external contacts. One or more dice can be wire bonded to the conductors, and protected by a plastic material, such as a glob top encapsulant. A ball grid array package has a peripheral outline that is on the order of two to eight times that of the die. While the size is an improvement over conventional packages, this type of package also requires relatively complicated manufacturing processes, and has not received widespread acceptance in the industry.
Yet another type of package is referred to as a chip scale package. Typically, a chip scale package includes a substrate bonded to a face of a single die. The substrate includes external contacts for the package, such as solder balls in a ball grid array (BGA), or in a fine ball grid array (FBGA). The substrate for a chip scale package can comprise a flexible material, such as a polymer tape, or a rigid material, such as silicon, ceramic, or a glass filled resin. A chip scale package has a peripheral outline that is about the same as that of the die contained within the package (e.g., 1.2.times.). However, volume manufacture of chip scale packages has proven to be difficult. In particular forming reliable electrical connections between the die and substrate requires specialized equipment and techniques.
The present invention is directed to a semiconductor package that is simpler in construction, and cheaper to volume manufacture than any of the above conventional packages. In addition, the package has a relatively small peripheral outline, but is designed for fabrication in a stacked configuration, in which multiple dice can be contained in the same package.